Random Access Memory (RAM)

Random Access Memory (RAM)

1. Commonly used term of memory is random access memory.
2. RAM holds temporary instruction and data needed to complete task.
3. When entire a command from the keyboard, it calls data from a storage device into memory, which can provide data to the CPU quickly.

Types of RAM:-

1. Static RAM (SRAM)
2. Dynamic RAM (DRAM)

Types of DRAM:-

1. Asynchronous Dynamic RAM (A sync DRAM)
2. Synchronous Dynamic RAM (sync DRAM)

SRAM:-

            RAM that holds it data without external refresh, for as long as power is supplied to the circuit. SRAM are used for specific application with in the PC. SRAM is superior then DRAM that’s why it is used for cache memory needs to be very fast and not very large. Advantage of SRAM is does not required, external refresh circuit to keep their data intact. SRAM is faster than DRAM. SRAM is expensive and it takes much more space (4 to 6 transistor).

DRAM:-

            DRAM is a type of RAM that only holds it data if it is continuously access by special logic called a refresh circuit. This circuitry reads contains of each memory cell whether the memory cell is being used at that time by the PC or not. All PC’s used DRAM for their main system memory even though it is slower compare to SRAM.

  

Asynchronous and Synchronous DRAM:-

1. Conventional DRAM has been used in PC’s seem the original IBM PC days is said to be Asynchronous DRAM.
2. Async memory is not synchronized with system clock
3. Its work fine in lower speed memory bus systems but it is not suitable for used in high speed memory system.
4. The newer type of DRAM is synchronous to the system clock.
5. All signals are tied to the clock so the timing is much tighter.
6. It is more suitable to the higher speed memory system of the newest PC.

Access Time:-

1. When a memory is read or written, this is called memory access.
2. Modern PC read or write 64 bit at a time, each read or write involves simultaneous access to as many as 64 different DRAM chip.
3. The amount of time that memory to produce the data, required from the start of the access until when the valid data is available for used is called the memory access time. It is normally measured in neon-second.

Memory Bus:-

1. It is a set of wire that is used to carry address last data to and from the system RAM.
2. The memory bus in most PC’s is also shared with processor bus; the memory bus is made up of 2 parts.
1. Data bus:-

This carried actual memory data within the PC.

2. Address bus: - It is used to select memory address that the will come from or goes to on a read or write (more band with better the performance) Hz.

RAM types by making (chips)

• Parity (Show error if RAM is damaged.)
• ECC (Error correction code)
• EDO (Extended data out)
• SDRAM
• SDRAM2 or DDR
• DDR2

*    RAM Bus

*    SLDRAM

Parity:-

1. First memory technology for first PC.
2. Checks all individual bits for data accuracy.
3. Slow type of DRAM.
4. Errors are detected and reported but may cause computer hang and data lose.

ECC:-

1. Memory technology for server computer.
2. Error detection and correction.
3. Capable of detecting individual bit (2, 3, 4) memory error and correct only one bit of error at a time.
4. ECC generally not used in desktop PCs.

CDO:-

1. Introduce in 1995 for multi tasking OS and application.
2. Allows read and write at the same time.
3. Focus for 64 bit processor.
4. 10 to 15 % faster access time under multi tasking OS and application.
5. No error detection and correction facilities.
6. Suitable only for stand alone PCs.

SDRAM:-

1. Introduce in 1997 for desktop PC.
2. Designed to synchronize itself with the time of the CPU.
3. This memory works with the parallel speed of the CPU.
4. Faster than earlier memory.
5. Available in several speeds i.e. 66MHz, PC100, and PC133 etc.

DDR:- 

1. Introduce in 2000 for desktop PC.
2. SDRAM memory supports one operation per clock cycle, DDR or SDRAM can perform (support to operation per clock cycle).
3. Over 2/3 of the memory shipped (sell and purchase) in 2003 was DDR.
4.  Used in many different platform, including desktop PC, server, note books, etc.
5. DDR memory is selected because of its increase of performance as well as low cost premium over SDRAM.
6. DDR memory deliveries increased memory band width and performance.
7. DDR dims have 184 pins.
8. DDR has different notch compare to other.
9.  Diagram of notch.
10. DDR module is not backward compatible. 

DDR2:-

1. DDR memory technology has matured and industry selects DDR2 to be next generation memory technology starting in 2004.
2. DDR2 memory technology is based upon DDR memory technology.
3. DDR2 feature faster speed, higher data band width lower power consumption and enhance thermal performance.
4. DDR2 are available in different platform using different form factor.
5. DDR2 has 240 pins.

RAM BUS (RDRAM):-

1. RD RAM chip introduced in 1999 for P4.
2. Developed by RAM BUS Inc.
3. Available for only P4 mother board and runs at up to 800 MHz bus speed.
4. Extra ordinary faster than older memory but was expensive.

Sink Link Dynamic RAM (SLDRAM):-

1. Developed by other DRAM chip manufacturer as an alternative to RAM bus.
2. Also focus for P4 and provides almost same feature as RAM Bus DRAM.

Single Inline Memory Module (SIMM):-

1.      Provide single data path.

2.      Available at 30 pins and 72 pins.

3.      Used up to 486 PCs.

4.      Provide 8 bit and 32 bit data output.

Dual Inline Memory Module (DIMM):-

1. Provide double data path and fast than SIMM.
2. Available at 186 pins for PCs.
3. Designed for Pentium processor and later used for P2, P3, P4.
4. Provide 64 bit data output.

Bank Schema:-

1. Arranging of memory in computers is called banks.
2. A bank schema is a diagram of rows and column that shows the no. of memory sluts in a system.

Before Upgrading Memory:-

1. Refer Documentation to Check:-
1. Bank schema.
2. No. of memory slot.
3. Free memory slot.
4. Exiting memory type and speed.
5. Memory size and module size.
6. Compatibility.

Troubles Shooting memory problem:-

Common Memory Problem:-

• Improper configuration.
• Improper installation.
• Defective memory module.
• Poor quality DRAM chip.
• Speed mismatch.

Basic Troubleshooting:-

1. Making sure you have right memory part.
2. Confirm memory is configured correctly.
3. Loose connections at slot.
4. Swap/interchange/ verify memory module.
5. Clean the slot and verify slot.
6. Update the DIOS incase of BUG (error).

Thank you,
 Ram Sharan Shretha
 Total Library